Organ tremolo



March 23, 1937. M, QUAVE 2,074,428

ORGAN TREMOLO Filed May 19, 1936 Patented Mar. 23, 1937 UNITED STATES:

PATENT OFFICE 6 Claims.

This invention relates to organ tremolos or devices for producing rhythmic variations in the pressure of the air supplied to the organ pipes.

Many different types of tremolos have been proposed but the only type which has been used generally has included some form of pulsating bellows for actuating a valve, or double disk valve, to vary the effective pressure at the pipes.

An object of this invention is to provide an organ tremolo of simple, rugged and inexpensive construction which will be reliable in operation and of longer life than prior types of tremolos. An object is to provide an organ tremolo which omits the usual pulsating bellows and includes, in place thereof, a spring or resilient clapper arm for actuating the valve mechanism for producing the fluctuations in air pressure. More specifically, an object is to provide an organ tremolo including a valve for controlling a vent in the air supply system, a spring or resilient clapper arm for actuating the valve, and an adjustable stop for regulating the action of the clapper arm, thereby to control the frequency of the air pressure fluctuations.

These and other objects and advantages of the invention will be apparent from the following specification when taken with the accompanying drawing in which:

Fig. 1 is a perspective view of an embodiment of the invention;

Fig. 2 is a substantially central longitudinal section through the same; and

Fig. 3 is a front elevation of the clapper arm and valve.

In the drawing, the reference numeral l identifies an oblong wooden box with air-tight joints at junctions of the back wall 2 with the end walls 3 and side walls 4, the box having a removable cover 5 secured in place over a cork packing 6 by screws 7. The box or casingv l is secured in vertical position to any suitable support by clips 8 that are fixed to the back wall 2.

The tremolo casing l is divided into two compartments by a partition 9 which has an aper- 45 ture ill, the efiective size of which is regulated by a slide ll which is held between two grooved pieces of wood I2. The aperture Ill is controlled by a hinged valve l3, covered with felt l4, and fastened by means of eyescrews to an air mo- .tor I6. This air motor consists of two wooden walls and a flexible part IT, a weak internal spring It being provided to assist it in opening. The

air motor communicates through port l9 either with the outside air or with the lower compart- 55 ment of the tremolo according to the position of the armature of the electric magnet 2|. The wiring of the electromagnet is of the usual type, with terminals 2i extending through the side wall l just above the magnet for connection to wires, not shown, one of which runs through the control tablet on the console to the generator and the other runs directly to the generator. Opening into the lower compartment of the trem- 010 is a conduit 22 which brings air under pressure from the well of the organ bellows, not 10 shown.

The exact construction of the motor actuated valve mechanism for admitting air into the upper compartment of the tremolo casing is not an important feature of the invention. The mecha- 15 nisrn for controlling the escape of air from the tremolo casing through the vent opening 23 in a side wall is, however, of major importance.

A thick spongy washer 24 is secured to the inner face of the wall 4 about the vent 23, and the control valve 25 carries a thick circular felt bumper or facing 26 for seating against the washer 24. A lead weight 21 may be secured to the inner face of the valve 25 by a bolt 28 and nut 23. The valve 25 may be attached to but, as shown, is preferably the integral end portion of resilient clapper arm 30 of wood or metal which has its lower and laterally enlarged end rigidly secured to the wall 4 by screws 3|.

As shown in Fig. 2, the normal position of the clapper arm is such that the facing 26 of valve 25 is spaced from the valve seat or washer 24 of the vent 23. This normal or unstressed position of the clapper arm 3%) is preferably approximately, though not necessarily, parallel to the side wall An adjustable abutment or flat-ended bumpor screw 3'2 is threaded into the side wall for cooperation with the clapper arm 30, and carries a lock nut 33 for securing the abutment screw in any desired position of adjustment.

When the tremolo is not in action, the parts stand in the positions shown in Fig. 2, i. e. compressed air from the bellows enters the lower compartment of the tremolo casing, but the upper compartment is vented to atmosphere as the port i=3 is closed and armature 20 is held by the air pressure against the vent of the magnet case. When the tremolo stop tablet is. tilted, the magnet 25 is energized, the motor is is collapsed as the armature moves to vent the passage l9 to atmosphere, and the valve i3 is thereby opened to admit air pressure to the upper compartment. The upper compartment is then rhythmically vented to atmosphere at a frequency which is determined by the adjustment of the bumper screw 32.

The operation or timing of the tremolo is adjusted in the following manner. The bumper screw 32 is first backed ofi to allow free movement of the clapper arm 30. The rush of air escaping through the vent 23 draws the valve 25 to the washer 24, and the pressure within the compartment retains the valve in closed position, i. e. the clapper arm 3!] is relatively weak and the initial position of valve 25 is so chosen that the stress set up in the clapper arm 3% by this flexing is not sufiicient to open the valve 25. The abutment screw 32 is then advanced into engagement with the clapper arm 30 to force the latter away from the side wall 4. As the bumper screw is advanced, a point is presently reached when the valve will be forced from the vent 23 and air will escape through it. The suction of this escaping air and the force of compressed air again forces the valve to its seat, closing the vent, but in doing so it bends resilient arm 38 at the end of screw 32 and the stress thus set up in the clapper arm forces the valve from the vent. This movement is repeated over and over, causing a rhythmic interruption of the large stream of air escaping at vent 23 and, consequently, substantial changes in the pressure within the tremolo casing. These pressure variations are transmitted through the conduit 22 and cause an oscillation of the bellows lid, and in the pressure of the air contained therein, and leading to the pipes. This rising and falling of pressure causes the beautiful wavering or quivering quality to the music.

If desirable, the regulating slide l2 may now be moved until the beat sounds its best, or the tremolo may be stopped and opened, and the mass of the lead weight '2'! may be increased to make the beat slower, or decreased to make the beat quicker, after which it is closed and regulated again. When the beat is at its best, the lock screw 33 is tightened.

To stop the tremolo, the tremolo tablet on the console is flipped to an off position. The current being cut ofi from the magnet, the armature 29 is driven against and closes the vent of the magnet, compressed air flows through the magnet, and hole l9 into air motor i6, and assists spring H2 in opening the motor and closing valve I4.

The tremolo, when adjusted for a desired frequency of vibration, maintains this adjustment for long periods. It is particularly to be noted that the frequency of vibration is not the natural resonant frequency of the resilient clapper arm. The movement of the clapper arm is a forced vibration determined by the adjustment of the abutment screw 32, and the frequency may therefore be adjusted to any desired value by regulating the bending stress which operates as a restoring force to move the valve 25 to open position. The construction is therefore distinguished from the vibrating reeds which have been proposed from time to time but which, so far as applicant is aware, have never operated satisfactorily.

It is to be understood that the invention is not limited to the particular embodiment herein illustrated and described, as many variations may be made in the parts, their relative size, shapes and positions without departing from the spirit of my invention as set forth in the following claims.

I claim:

1. In an organ tremolo, a tremolo casing and a valve-controlled conduit for placing the same in communication with the system supplying air for sounding the pipes, a vent opening through a wall of said casing, a valve cooperating with said vent opening, a resilient clapper arm within and having one end secured to said tremolo casing, said valve being carried at the other end of said clapper arm, and an abutment positioned in the path of movement of an intermediate portion of said clapper arm when the latter is flexed as the air escaping through said vent opening moves the valve to closed position, whereby the clapper arm is bent over said abutment to produce a restoring force operative to open said valve against the pressure within said tremolo casing.

2. In an organ tremolo, a tremolo casing and a valve-controlled conduit for placing the same in communication with the system supplying air for sounding the pipes, a vent opening through a wall of said casing, a valve cooperating with said vent opening, a resilient clapper arm within and having one end secured to said tremolo casing, said valve being carried at the other end of said clapper arm, and an abutment adjustably mounted on said tremolo casing in the path of movement of an intermediate portion of said clapper arm when the latter is flexed as the air escaping through said vent opening moves the valve to closed position, whereby the clapper arm is bent over said abutment to produce a restoring force operative to open said valve against the pressure within said tremolo casing.

3. An organ tremolo of the type including an air pressure compartment adapted to be placed in communication with the bellows of the organ, a vent for said compartment, and valve means for rhythmically opening and closing said vent, characterized by the fact that said valve means comprises a resilient clapper arm within said compartment and carrying a valve for closing the vent, the clapper arm being relatively weak and incapable of opening the valve against the pressure within the casing when the valve is seated by the escape of air through the vent, and means for establishing in said clapper arm as the valve moves to vent-closing position a force for restoring the valve to open position.

4. An organ tremolo comprising a casing having a vent opening, means for admitting air to said casing, a clapper arm vertically arranged in said casing and having its lower end rigidly secured thereto, a valve at the upper end of said casing in alinement with and normally spaced from said vent opening, said clapper arm being flexible to permit automatic closing of said valve by the air as it escapes through said vent opening and relatively weak, and an abutment mounted on said casing in the path of flexing movement of said clapper arm when the valve moves to vent-closing position, whereby the clapper arm bends about said abutment.

5. An organ tremolo as claimed in claim 4, wherein'said abutment includes means for varying the position thereof to control the extent of the bending of said clapper arm, and means for retaining the abutment in any desired position of adjustment.

6. An organ tremelo as claimed in claim 4, wherein said abutment comprises a screw threaded through a wall of the casing, and a lock nut for retaining the screw in any desired position of adjustment.

r GEORGE M. QUAVE. 

